The present invention relates generally to mobile grain harvesting machines and more particularly to an axial flow combine in which improved means are provided for guiding crop materials along a predetermined path.
During field operation of a mobile combine harvester, grain is threshed, separated, cleaned and delivered for transport from the field. Over the past 30 years, the threshing function in most commercially available combines has been carried out by a rotating threshing cylinder, cooperatively associated with a concave extending transversely to the direction of combine travel. Crop material is fed to the forward edge of the concave, and passed along a generally longitudinal path between the concave and rotating cylinder. Some grain is discharged through the concave while the remaining crop material is discharged over the trailing edge of the concave onto straw walkers that extend rearwardly across the combine. Grain, separated from the chaff on the reciprocating walkers is deposited on cleaning sieves and eventually collected and conveyed to a grain tank, while the straw residue is advanced rearwardly and expelled onto the field. This type of harvesting equipment commonly referred to as a conventional combine, is more thoroughly described in the prior art, exemplary of which are U.S. Pat. Nos. 3,411,274 and 3,472,235.
During the lengthy period of mobile combine development many other types of combines have been considered but for the most part with a lesser degree of success than the conventional combine. For example, U.S. Pat. No. 2,825,455, issued Mar. 4, 1958, to W. Streich et al, shows a combine in which a conventional threshing cylinder and concave are utilized in combination with a longitudinally extending rotary drum separator in place of conventional straw walkers. Another example of the many and varied arrangements in the prior art is shown in U.S. Pat. No. 2,811,158 issued Oct. 29, 1957, to O. Rietman. In the Riethman patent, a conventional concave and threshing cylinder are again shown in combination with a separation structure utilizing a drum mounted along an axis aligned with the path of combine travel.
Recently, a new and significantly different combine design has been developed and has met with outstanding commercial success. This combine, described in many patents that have issued over the past several years, comprises two side-by-side generally cylindrical crop handling units each having tandem threshing and separating sections. During operation crop material is conveyed to the crop handling units and thence advanced in a generally axial direction along two separate helical paths in the cylindrical units. Exemplary of this type of axial flow combine is U.S. Pat. No. 3,742,686 issued on July 3, 1973, in the name of E. W. Rowland-Hill and assigned to the assignee of the present application. During operation, grain is separated from crop material and discharged through concaves and grates in the threshing and separating sections, respectively, onto a grain pan below the cylindrical units. The grain is in turn deposited on cleaning sieves and thence elevated by an auger to a storage tank mounted on the combine. Meanwhile, the residue is conveyed rearwardly and expelled onto the field. this design, which has reduced grain losses, minimized grain damage and increased overall capacity and reliability, is believed to be the most efficient high performance commercially avaialbel combine known in the art. Among the many things contributing to this success is the effective utilization of centrifugal force in the separation section. Grain is discharged outwardly through separation grates as the crop material is transferred rearwardly along its axial path.
Combines with a single cylindrical crop handling unit for accomplishing threshing and separating have also been considered in the past. Although this type of combine has been disclosed in various patents it is not commercially available. An example of a single cylinder crop handling machine is shown in U.S. Pat. No. 3,481,343, issued to E. M. Van Buskirk on Dec. 2, 1969. In the Buskirk machine material is fed into the front end and advanced rearwardly in a generally axial direction along a path between a rotating rotor and the cylindrical casing in which tandem threshing and separating sections are embodied. This type of combine is commonly referred to as a single rotor axial flow combine in contradistinction to the double rotor machine described in U.S. Pat. No. 3,742,686, mentioned above.
In prior art axial flow combines, it is common in machines where centrifugal separation is employed for the separating section to discharge material over a limited portion of its area. In the remaining portion of the cylindrical surface area guiding vanes extend from impervious walls to assist in the rearward helical advancement of the crop material during the separation process. Various other prior art arrangements of vanes and crop engaging elements have been utilized to urge material rearwardly along a generally axial path in machines where grain is separated from crop material. Included among these arrangements is a stationary cylindrical corn sheller, shown in U.S. Pat. No. 1,777,992, issued on July 15, 1932, to J. Lizamore, in which material is fed into a hopper and shelled in a separation drum having helical segments to assist in the removal of kernels of corn from the cobs during the shelling process. Another approach is shown in U.S. Pat. No. 2,842,266 issued to E. C. Carlson on July 8, 1958, wherein a cylindrical separation mechanism having internal and external flighting is employed to convey crop material along a path in a generally axial direction.